Refrigeration apparatus and method



Dec. 12, 1939.

C. F. ALSING REFRIGERATION APPARATUS AND METHOD 3 Filed April 1 1957 Q nsssune DROP 75c; m.

LENGTH OF CRPILL'HRY TUBES F'J 6.3 INVENTOR CARL F". FlL-SING BY ATTOR Y Patented Dec. 12, 1939 REFRIGERATION APPARATUS AND METHOD Carl F. Alsing, Springfield, Mass, assignor to Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 1, 1937, Serial No. 134,231

'- 13 Claims.

My invention relates to refrigeration apparatus and method of operating the same and particularly to the control of the flow of refrigerant between the high pressure and low pressure portions of such apparatus. I

In order to control the flow of refrigerant between the high pressure side of a refrigerating system, of which the condenser is a part, and the low pressure side, of which the evaporator is a part, a tube of considerable length and relatively small diameter, sometimes referred to as a "capillary tube has been heretofore utilized. One of the principal disadvantages of a capillary tube for this purpose is that it depends primarily on the difference in pressure between the ends thereof for regulating the flow of refrigerant. It is, therefore, apparent that in a refrigerating system, for example of the type wherein the condenser is air-cooled and the evaporator is subjected to varying heat loads, as in the usual domestic refrigerator, the pressure drop across the tube varies considerably, with the result that the flow of liquid refrigerant through the tube changes. For example, if the capillary tube is designed to operate in a room temperature of F. and in a refrigerator cabinet wherein the air is normally maintained at 45 F., an increase in condenser temperature with consequent increase in pressure will result in forcing an excessive amount of gas through the tube. Likewise, a decrease in cabinet air temperature with consequent decrease in evaporator pressure and decrease in amount of refrigerant pumped will result in an excessive amount of gas being forced through the capillary tube. This results in a loss in efflciency, since the gas is merely circulated throughout the system and reduces the usefulnessof the work of the compressor.

If the temperature of the air surrounding the condenser decreases below 80 F. with subsequent decrease 'in condensing temperature, the amount of liquid refrigerant passed by the capillary tube will temporarily decrease and liquid will back up into. the condenser with consequent increase in condensing pressure above a value desirable at this room temperature. This will result in the loss in efliciency of the system and in addition the pull-down characteristics of the system, that is, the amount of time and work necessary to bring the cabinet down to the desired temperature are also deleteriously effected because the evaporator is starved and the machine is working less efficiently.

If the temperature of the air in the cabinet increases above 45 F. with consequent increase in suction pressure, the amount of refrigerant pumped by the compressor will increase but the amount of liquid passed by the capillary tube will not increase sufficiently to take care of the increase in liquid pumped. This also results in starving the evaporator and increasing the discharge pressure with consequent loss in emciency andundesirable effect on the pull-down characteristics of the system.

It is, therefore, an object of my invention to improve the operation of a capillary tube flow restrictor for a refrigerating system.

It is another object of my invention to pass refrigerant to the evaporator at such a rate that liquid will not appreciably back up into the condenser nor will excessive amounts of gas be passed through the capillary tube.

It is a further object of my invention to change the flow retarding effect of a capillary tube flow restrictor in response to changes in condenser and/or evaporator pressures to effect the change in flow retardation progressively in response to changed conditions within the system.

It is still a further object of my invention to vary the flow retarding effect of a capillary tube flow restrictor by abstracting heat therefrom in in response to changed conditions within the refrigerating system, and, furthermore, to accomplish this result by utilizing the refrigerant in the system for abstracting said heat.

It is another object of my invention to materially improve the efliciency of a refrigerating system utilizing a capillary tube, and to provide an improved construction and method of operation for such a system.

These and other objects are effected by my invention, as will be apparent from the following description and claims, taken in connection with the accompanying drawing, forming a part of this application, in which:

Fig. 1 is a diagrammatic view of a refrigerating system embodying my invention;

Fig. 2 is an enlarged sectional view of the discharge end of the two tubes which supply liquid refrigerant to the evaporator; and,

Fig. 3 is a curve showing the pressure drop in relation tothe length of the capillary tubes utilized in my invention. 3

Referring specifically to the drawing for a detailed description of my invention, numeral ll designates a compressor which is driven by a motor l2 through a shaft l3. While I have shown my invention as applied to compression type refrigeration apparatus it is not limited to such apparatus, but is applicable to all types of refrigerating systems in which a volatile fluid is condensed and then evaporated to abstract heat. Gas compressed by the compressor II is conveyed through a conduit I4 to a condenser ll shown as an air cooled condenser by way of example, wherein the compressed refrigerant gas is condensed by the cooling action of air forced over the condenser by a fan It. Condensed refrigerant is then conveyed to an evaporator l'l, wherein it vaporizes-and withdraws heat from the air in a refrigerator compartment i8, and the vaporized refrigerant is conveyed back to the compressor through a conduit i9, whereupon the cycle is repeated. A suitable electrical control 2|, many types of which are well known, controls energization of the motor l2 from a source of electrical power L1, L2, in response to demands from the evaporator I! for cooling. A suitable bulb 22 ,and bellows 23 filled with an expansible fluid is associated with the evaporator I1 and is responsive to temperature variations thereof. A spring 24 opposes the force exerted by the bellows, and is adjustable by means of the mechanism indicated at 25, so that the average evaporator temperature may be varied at the will of the user.

As shown in Fig. 1, liquid refrigerant from the condenser I5 is conveyed to a chamber 21, the purpose of which is fully described hereinafter. From the condenser, liquid refrigerant normally passes through a coiled capillary tube 28 to the evaporator IT. This tube is connected adjacent the bottom of the chamber 21 and is preferably of considerable length, for example, 10 feet and of restricted diameter, such as, for example, .04 inch. In accordance with my invention, if the average conditions to which the refrigerating system is subjected are F. ambient air and somewhat higher condensing temperature, and 45 F., air in the refrigerator cabinet, the capillary tube 28 is designed to operate at a higher ambient temperature, such as for example, F., and a lower refrigerator cabinet temperature, for example 35 F. This may be accomplished by either increasing the length of the tube, or decreasing the bore. The tube thus designed obviously will offer more resistance to the flow of refrigerant than the optimum desired for lower cabinet and room temperatures. However, by utilizing my invention, liquid is conveyed from the condenser to the evaporator under all normal operating conditions in such a manner that the chamber 21 remains substantially filled with liquid but liquid does not back up into the condenser nor is gas passed by the capillary tube in appreciable quantities.

In order to effect this desirable operation, it is necessary to change the resistance to the flow of liquid in the capillarytube 28 in response to changing conditions in the refrigerating system. I therefore provide a second capillary tube 3| of, for example, 15' in length and somewhat less than .04" in diameter so that the restriction to the flow of liquid therethrough will be appreciably more than the restriction to the flow of liquid through the capillary tube 28. The second capillary tube 3| connects with the top of the chamber 21. At the end of the capillary tube 3| a short length of capillary tube 32 for example two feet in length and .06 of an inch in diameter connects with the evaporator l1 and is disposed in heat exchange relation with a portion 30 of the lower capillary tube 28, which portion 30 is at the end of the capillary tube 28 adjacent the evaporator II. It is to be noted that the tubes 3| and 32 may be considered as a part of the chamber 21 since the purpose of the tubes 3| and 32 is not primarily to convey refrigerant from the tank 2! to the evaporator I! but is to change the restriction to the flow of liquid through the capillary tube 28 under various operating conditions. It is obvious that the tubes 3| and 32 will pass very little refrigerant to the evaporator I1 because of the relatively great restriction offered by these tubes with respect to the capillary tube 28.

At the 110 room and 55 cabinet temperature, the tank 21 will be substantially filled with liquid but very little if any liquid will be passing through the tubes 3| and 32 since the capillary tube 28 is designed to pass the amount of liquid condensed to the evaporator under these conditions.

The chart shown in Fig. 3 illustrates the effect of cooling the end of the capillary tube 28. The curve marked A" in Fig. 3 illustrates the expansion of liquid passing through the capillary tube 28 when the portion 30 of the capillary tube 28 is cooled by refrigerant in the capillary tube 32. The curve marked B illustrates the expansion of the liquid in a capillary tube such as the tube 28 which does not have heat abstracted therefrom near its end. From these curves it will be clear that the majority of expansion in a capillary tube takes place adjacent the outer end thereof, at which time gas is formed and the restriction of the tube increases rapidly. By cooling the capillary tube, as explained hereinafter, less expansion of liquid takes place at the end thereof and the restriction to the flow of liquid through the, capillary tube may, therefore, be varied by varying the amount of heat abstracted from the outlet end thereof.

Assuming now that the condensing pressure drops because the ambient temperature has dropped to 60 F. This decrease in discharge pressure would normally result in decreasing the flow of liquid through the capillary tube, and, since more refrigerant is being condensed at the lower room temperature, liquid would tend to back up into the condenser and increase the discharge pressure to a higher value than is desirable at the 60 room temperature. However, at this time the level of the refrigerant in the tank 21 will rise more rapidly and a relatively large quantity of refrigerant will pass through the capillary tubes 3| and 32 with the result that the end of the capillary tube 28 will be subcooled considerably. This will reduce the restriction to the flow of refrigerant through the capillary tube 28 to such a point that all the liquid condensed will pass through the capillary tube 28 with the exception of the slight amount of refrigerant which has increased the level in the tank 21 and which has passed through the capillary tubes 3| and 32. If the ambient temperature now rises to, for example, 80 F. slightly less refrigerant will be condensed than at the 60 'F. condition because of lower volumetric efficiency. of the compressor and increased condensing temperature and less refrigerant will be passed through the capillary tubes 3| and 32 with the result that the refrigerant passed through the capillary tube 28 is decreased because the end thereof is not cooled as much as it was under the 60 F. room conditions. Slightly less refrigerant will, therefore, pass through the capillary tube 28, but the amount will be equal to the amount pumped by the compressor, and gas will not be forced through the tube 28 because the inlet end thereof will be immersed in liquid.

Assuming now that the cabinet air temperature drops to 35 this will result in less refrigerant being pumped by the compressor with the result that the level in the tank 21 will drop considerably and without my invention, the liquid in the tank 21 would be exhausted and the capillary tube 28 would pass gas rather than liquid. However, by utilizing my invention, less refrigerant is passed through the capillary tubes 3i and 32 at the 35 cabinet condition. This results in the end of the capillary tube 28 being cooled to a less degree so that the restriction of thetube will increase. This will also increase the level of the liquid in the tank 21 so that the end of the tube 28 will always be covered with liquid and gas will not be passed, in the same manner as explained with respect to increased discharge pressure. If the cabinet air temperature rises to F., slightly more refrigerant will be pumped but will not collect in the condenser and raise the discharge pressure unduly because more refrigerant will be passed by the capillary tubes 3| and 32 than at the 35 F. condition with the result that that end of the capillary tube 28 will have more heat abstracted therefrom, the restriction to the flow of liquid through the capillary tube 28 will decrease and the capillary tube 28 will therefore pass the increased amount of refrigerant being pumped. I i

It will be apparent therefore that by utilizing my invention the proper amount of refrigerant is maintained at all times in the condenser and in the evaporator and the capillary tube 28 will pass substantially the amount of liquid which is being pumped by the compressor and will not pass any gas. It will also be obvious that by utilizing my invention, the resistance to the flow of liquid through the capillary tube is progressively varied in response to changing conditions in the system such as increased or decreased discharge pressure and increased or decreased suction pressure. these conditions may change at the same time, that is, for example, the discharge pressure may rise and at the same time the suction pressure may rise. However, the system is so designed that under any changing conditions the capillary tube will function as though it were designed for that particular condition. It will therefore be apparent that I have provided improved refrigeration apparatus utilizing a capillary tube flow restrlctor between the condenser and the evaporator.

While I have shown my invention in but one form, it will be obvious to those skilled in the art that it is not so limited, but is susceptible of various changes and modifications without departing from the spirit thereof, and I desire, therefore, that only such limitations shall be placed thereupon as are imposed by. the prior art or as are specifically set forth in the appended claims.

What I claim is:

1. In refrigeration apparatus, the combination of a condenser, an evaporator, means for circulating refrigerant to the condenser for liquefac-' tion therein and to the evaporator for vaporization and the withdrawal of heat therefrom, a

flow restriction device disposed between the condenser and the evaporator and comprising a tube of considerable length and relatively small diameter, and a device comprising a chamber for liquefied refrigerant disposed between the condenser and said evaporator and embodying a portion in heat exchange relation with said tube- It will also be apparent that- 2. In refrigeration apparatus, the combination. of a high pressure portion including a condenser, a low pressure portion including an evaporator, means for circulating refrigerant to the condenser for liquefaction therein and to the evaporator for vaporization and the withdrawal of heat therefrom, a flow restriction device disposed between the condenser and the evaporator and comprising a tube of considerable length and relatively small diameter, and a device for varying the flow of refrigerant through said tube comprising a chamber for liquefied refrigerant disposed between said condenser and said evaporator and embodying a second tube connecting the chamber with the low pressure portion of the system, said second tube being of more restriction to the flow of refrigerant liquid than the first1 tube and in heat exchange relation therewi 3. In refrigeration apparatus, the combination of a refrigerator cabinet embodying a space to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said cabinet, said condenser forming a portion of a high pressure side of the system, means for circulating refrigerant to the condenser for liquefaction therein and then to the evaporator for vaporization therein, a tube of considerable length andrelatively small diameter for restricting the flow of refrigerant between the condenser and the evaporator, and means disposed in heat exchange relation with said tube for varying the flow of refrigerant therethrough in response to changes in temperature of the space to be cooled and in response to changes in temperature of said ambient air.

4. In refrigeration apparatus, the combination of a refrigerator cabinet. embodying a space to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said cabinet, said condenser forming a portion of a high pressure side of the system, means for circulating refrigerant to the condenser for lique-.

faction therein and then to the evaporator for vaporization therein, a tube of considerable length and relatively small diameter for restricting the flow of refrigerant between the condenser andthe evaporator, and means for varying the flow of refrigerant through said tube in response to changes in condenser pressure, said last means embodying a chamber for collecting liquid refrigerant having a portion thereof in heat exchange relation with said tube, and a connection between said chamber and the low pressure portion of the system for effecting vaporization of refrigerant in said heat exchange portion so as to withdraw heat from said tube.

5. In refrigeration apparatus, the combination of a refrigerator cabinet embodying as'pace to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said for varyingthe flow of refrigerant therethrough.

cabinet, said condenser forming a portion of a high pressure side of the system, means for circulating refrigerant to the condenser for liquefaction therein and then to the evaporator for vaporization therein, a tube of considerable length and relatively small diameter for restricting the flow of refrigerant between the condenser and the evaporator, and means for varying the flow of refrigerant through said tube in response to changes in evaporator pressure, said last means embodying a chamber for collecting liquid refrigerant having a portion thereof in heat exchange relation with said tube, and a connection between said chamber and the low pressure portion of the system for effecting vaporization of refrigerant in said heat exchange portion so as to withdraw heat from said tube.

6. In refrigeration apparatus, the combination of a refrigerator-cabinet embodying a space to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said cabinet, said condenser forming a portion of a high pressure side of the system, means for circulating refrigerant to the condenser for liquefaction therein and then to the evaporator for vaporization therein, a tube of considerable length and relatively small diameter for restricting the flow of refrigerant between the condenser and the evaporator, and means disposed in heat exchange relation with said tube for varying the flow of refrigerant through said tube in response to changes in condenser pressure, said last means embodying a chamber disposed between sad condenser and said tube for collecting liquid refrigerant, and a second tube of less restriction than the first tube connecting said chamber and the low side of the system, said first tube connecting the bottom of said chamber with said evaporator and said second tube connectng the top of said chamber with said evaporator, said chamber normally containing liquid refrigerant, the level of refrigerant in said chamber being raised when the condensing pressure decreases, whereby the level in the chamber rises and more refrigerant passes through the second tube to said evaporator and vaporizes therein during its passage, said tubes being disposed in heat exchange relation, whereby heat is abstracted from said first tube and the flow resistance of the refrigerant insaid tube thereby decreased to compensate for the smaller amount of refrigerant being forced through said first tube.

7. In refrigeration apparatus, the combination of a refrigerator cabinet embodying a space to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said cabinet, said condenser forming a portion of ahigh pressure side of the system, means for circulating refrigerant to the condenser forliquefaction therein and then to the evaporator for vaporization therein, a tube of considerable length and relatively small diameter for restricting the flow of refrigerant between the condenser and the evaporator, and means for varying the flow of refrigerant through said tube in response to changes in condenser pressure, said last means embodying a chamber disposed between said condenser and said tube for collecting liquid refrigerant, and a second tube of less restriction than the first tube connecting said chamber and the low side of the system, said first tube connecting the bottom of said chamber with said evaporator and said second tube connecting the top of said chamher with said evaporator, said chamber normally containing liquid refrigerant, the level in said chamber being raised when the evaporator pressure increases, whereby the level of refrigerant in said chamber rises and more refrigerant passes through the second tube to said evaporator and vaporizes therein during its passage, said tubes being disposed in heat exchange relation, whereby heat is abstracted from said first tube to increase the amount of refrigerant being forced through said first tube to equal the increase in the amount of refrigerant circulated by said circulating means due to said increase in evaporator pressure.

8. In refrigerating apparatus, the combination of a condenser, an evaporator, means for circulating refrigerant to the condenser for liquefaction therein and to the evaporator for vaporization and the withdrawal of heat therefrom, a flow restriction device disposed between the condenserand the evaporator comprising a tube of considerable length and relatively small diameter, and a device disposed in heat exchange relation with said tube for withdrawing varying amounts of heat from a portion thereof to progressively vary the flow retarding effect of the tube, said device comprising a chamber for liquefied refrigerant disposed between said condenser and said evaporator and a second tube of considerable length and relatively small diameter connecting the chamber and the low pressure portion of the system, said second tube being of more restriction to the flow of refrigerant liquid than the first tube' and in heat exchange relation therewith.

9. In refrigerating apparatus, the combination of a condenser, an evaporator, means for circulating refrigerant to the condenser for liquefaction therein and to the evaporator for vaporization and the withdrawal of heat therefrom, a flow restriction device disposed between the condenser and the evaporator comprising a tube of considerable length and relatively small diameter, and a device for withdrawing varying amounts of heat from a portion thereof to vary the flow of refrigerant therethrough, said device comprising a chamber of liquefied refrigerant disposed between said'condenser and said evaporator, a second tube of slightly more length and substantially the same diameter as the first tube and a third tube of relatively short length and increased diameter disposed between the end of the second tube and the evaporator, said second and third tubes connecting said chamber with the evaporator and said third tube being in heat exchange relation with the portion of the first tube adjacent the evaporator.

10. In refrigeration apparatus, the combination of a refrigerator cabinet embodying a space to be cooled, an evaporator for abstracting heat from said space and forming a portion of a low pressure side of the system, a condenser disposed exteriorly of the cabinet and subject to the temperature of the ambient air surrounding said cabinet, said condenser forming a portion of a high pressure side of the system, means for circulating refrigerant to the condenser forliquefaction therein and then to the evaporator for vaporization therein, a tube of considerable length and relatively small diameter for restricting the flow of refrigerant between the condenser and the evaporator, a chamber disposed between said condenser and said tube for collecting liquid refrigerant, and a second tube of more restriction than the first tube connecting said chamber and amass:

the low side of the system, said tube connecting the bottom of said chamber with said evaporator and said second tube connecting the top of said chamber with said evaporator, said chamber normally containing liquid refrigerant and passing a predetermined amount of liquid refrigerant through said second tube and the level in said tank being varied by changes in pressure in the system to pass varying amounts of refrigerant liquid through said second tube to abstract varying amounts of heat from said first capillary tube to vary the flow of refrigerant therethrough.

11.- The method of operating a refrigerating system having a condenser and an evaporator maintained at different varying pressures and a capillary tube flow restrictor for regulating the flow of refrigerant from the condenser to the evaporator, which method comprises disposing the capillary tube in heat exchange relation with a quantity of refrigerant liquid, evaporating some of the last-mentioned refrigerant liquid to abstract heat from said tube, and progressively increasing the amount of refrigerant liquid in heat exchange relation with said capillary tube in response to changes in pressure in the evaporator and the condenser.

12. In a mechanical refrigerator, the combination of an evaporator, a tank for a refrigerant liquid, a capillary tube for conducting and retarding the flow of the refrigerant from said tank to said evaporator, said tank and capillary tube beingin unrestricted communication at all times,

said tube constituting substantially the sole retardation to said flow, and means responsive to the liquid level of the refrigerant in said tank for varying the retarding effect of said tube on the flow of said refrigerant through said tube.

13. In a mechanical refrigerator, the combination of an evaporator, a tank for a refrigerant liquid, a capillary tube for conducting and retarding the flow of refrigerant from said tank to said evaporator, and means responsive to the liquid level in said tank for cooling said capillary tube to vary the flow of refrigerant therethrough.

CARL F. ALSING. 

